Abstract

Although guidelines exist for approaches to, and vehicle use (over-snow vehicles,aircraft and watercraft) in the vicinity of, Weddell seals (Leptonychotes weddellii),there has been no scientific assessment of the effectiveness of these guidelines inminimising disturbance to the seals. This study examined tqe response of Weddellseals to various forms of human activity that the seals are currently exposed to. Aseries of controlled experiments were conducted to measure, (i) the immediatebehavioural and physiological responses of lactating W ~ddell seals (and their pups)to approaches on foot, and the factors affecting the seals' respons~, (ii) the temporal( -nature of the seals' response to repeated pedestrian activity fil?.d (iii) the immediatebehavioural response oflactating cows to over-snow vehicle operations, and thefactors that affect their response. In addition, sound/distance profiles were developedfor commonly used Antarctic vehicles ~d the assumed detection threshold ofWeddell seals was determined to investigate whether the noise generated by a rangeof vehicles had the potential to affect Weddell seals.Most lactating Weddell seals and lone pups responded to visits on foot {from 20-5 m from the seals) by becoming alert. The separation distance at which the cowsbecame alert was dependent upon the approach type (a single person or group ofpeople), the distance a cow was from the water, the distance she was from aconspeci:fic, and whether her pup was exposed (i.e. whether the pup was between theapproachers and the cow). The relative importance of these factors indicated that the-seals perceived pedestrians to be a threat, but that the level of threat was low.Regular and frequent approaches by a single person to lactating Weddell seals overa short time period(< 2 hours) produced evidence of rapid habituation. However,irregular approaches over a longer time period (~3 weeks), did not result in sealsshowing any sign of having habituated. The results suggested that the cows mayhave already become sensitised to human activity prior to the experiment and thatpups became sensitised to pedestrian activity.Onshore heart rate of the seals in the absence of people revealed a daily periodicityin rate as well as three distinct heart rate patterns during resting behaviour and whenthe seal was looking in the water, i.e. the seal has its head immersed in water. Intraseal variation in heart rate highlighted the importance of obtaining baseline data at afine scale (e.g. hourly) before heart rate can be used as a proxy for stress in human-wildlife interactions studies. Pedestrian approaches to a lactating seal did not elicit aheart rate response, suggesting that the approaches were not considered to benegative stimuli.Most lactating Weddell seals responded to the operation of over-snow vehicles bybecoming alert. Response was dependent upon the distance at which the vehicleswere driven, the position of the pups in relation to the cow and the distance the cowwas from the water. The relative importance of these factors indicated that the sealsperceived the vehicles to be a threat, but that the level of threat was low.Quantifying the effect of noise on the vocal behaviour of Weddell seals requiredthe development of an assumed detection threshold of the species and sound/distanceprofiles of the commonly used vehicles in Antarctica. Much of the noise generatedby these vehicles at the tested distances and speeds was barely audible to seals.However, there were some instances where the noise would have been cl~arly audibleto seals both hauled out on ice and underwater. These higher noise levels were,however, still below the noise levels generated by the animals themselves and weretherefore not expected to cause physical damage to the seals.- Manipulativeexperiments did indicate th~t the underwater vocal behaviour of Weddell seals couldbe affected by continuous Hagglund noise, manifest as a decrease in the calling rateof seals.This study has shown that the existing guidelines used in the Australian AntarcticTerritory could be improved ifthe goal of management is to minimise disturbance toWeddell seals. Furthermore, the study has shown that the responses of the seals wereinfluenced by a number of factors and that these co_uld be incorporated into visitorand operational guidelines in order to increase their effectiveness and sensitivity.

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Additional Information:

For consultation only. No copying permitted until 17th June 2007. Thesis (Ph.D.)--University of Tasmania, 2005. Includes bibliographical references